imx: kontron-sl-mx8mm: Increase CONFIG_SYS_CBSIZE to 2K

This allows using the command line with longer lines like
large scripts in env variables.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/configs/kontron-sl-mx8mm_defconfig b/configs/kontron-sl-mx8mm_defconfig
index ff306cd..0a7b5cc 100644
--- a/configs/kontron-sl-mx8mm_defconfig
+++ b/configs/kontron-sl-mx8mm_defconfig
@@ -48,7 +48,7 @@
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x58000
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SPL_ATF=y
-CONFIG_SYS_CBSIZE=256
+CONFIG_SYS_CBSIZE=2048
 CONFIG_SYS_PBSIZE=276
 CONFIG_CMD_NVEDIT_EFI=y
 # CONFIG_CMD_LZMADEC is not set